Production of trifluorovinyl ethers

ABSTRACT

A two step process, each of the steps being novel, for the production of trifluorovinyl ethers by reaction of a siloxane with selected acyl fluorides or carboxylic anhydrides, is disclosed. Also disclosed is a novel silyl ester intermediate.

FIELD OF THE INVENTION

Disclosed herein is a novel process for making trifluorovinyl ethers byreacting selected acyl fluorides or anhydrides with siloxanes, and thenthermolyzing the resulting silyl ester to form the trifluorovinyl etherand a fluorosilane. The fluorosilane may be recycled to siloxane.

TECHNICAL BACKGROUND

Trifluorovinyl ethers are used commercially as comonomers in polymers,particularly as comonomers in highly fluorinated polymers which areoften chemically and/or thermally relatively stable. The ethers areusually made by the gas or liquid phase thermolysis of the correspondingacyl fluoride over a bed of reactant and/or promoter. However, thesereactions often give only fair yields of the trifluorovinyl ether andtend to generate relatively large amounts of toxic waste, which aredifficult and expensive to dispose of. In the novel process describedherein, particularly when run under the preferred conditions, goodyields of the desired trifluorovinyl ether are obtained, and littletoxic waste is generated, as most of the byproducts can be recycled inthe process, and/or are otherwise useful.

J. D. Citron, J. Organometal. Chem., vol. 30, p. 21-26 (1971) reported(in Table 1 therein) that siloxanes reacted with acyl fluorides to formcarboxyl anhydrides and fluorosilanes.

SUMMARY OF THE INVENTION

This invention concerns a process for the production of trifluorovinylethers, comprising:

a) reacting a compound containing the group --O(C₂ F₄)COF or the group--O(C₂ F₄)C(O)O(O)C(C₂ F₄)O-- with a siloxane;

b) heating the silyl ester in the presence of a thermolysis catalyst, ata temperature of about 140° C. to about 350° C. to produce atrifluorovinyl ether and a fluorosilane; provided that where b) iscarried out in the gas phase, said thermolysis catalyst is not a diarylsulfone.

This invention includes a process for the production of silyl esters,comprising, reacting a compound of the formula R¹ [O(C₂ F₄)COF]_(z) or acompound of the formula R¹ [O(C₂ F₄)C(O)O(O)C(C₂ F₄)O]_(z) R¹ with asiloxane, to form a silyl ester, and wherein:

R¹ is a hydrocarbyl or substituted hydrocarbyl radical having z freevalencies; and

z is 1 or 2.

This invention also concerns a process for the production of atrifluorovinyl ether, comprising, heating a silyl ester of the formulaR¹ [O(C₂ F₄)C(O)OSiR² ₃ ]_(z), in the presence of a thermolysiscatalyst, at a temperature of about 140° C. to about 350° C., to producea trifluorovinyl ether and a fluorosilane, and wherein;

R¹ is a hydrocarbyl or substituted hydrocarbyl radical having z freevalencies;

each R² is independently hydrocarbyl, substituted hydrocarbyl or anoxysilyl group; and

z is 1 or 2;

provided that when carried out in the gas phase said thermolysiscatalyst is not a diaryl sulfone.

This invention also includes a silyl ester of the formula R¹ [O(C₂F₄)C(O)OSiR³ ₃ ]_(z), wherein:

R¹ is a hydrocarbyl or substituted hydrocarbyl radical having z freevalencies;

each R³ is independently hydrocarbyl, substituted hydrocarbyl, oroxysilyl; and

z is 1 or 2.

DETAILS OF THE INVENTION

This invention deals with a process for producing trifluorovinyl ethersfrom selected acyl fluorides or carboxylic anhydrides. The processinvolves two steps, each of which is novel, and a novel intermediate isinvolved. The chemical reactions are believed to be:

    --O(C.sub.2 F.sub.4)COF+≡SiOSi≡→--O(C.sub.2 F.sub.4)C(O)OSi≡+SiF                                (1)

    --O(C.sub.2 F.sub.4)C(O)O(O)C(C.sub.2 F.sub.4)O--+≡SiOSi≡→2--O(C.sub.2 F.sub.4)C(O)OSi≡(2)

    --O(C.sub.2 F.sub.4)C(O)OSi≡→--OCF=CF.sub.2 +CO.sub.2 +≡SiF                                               (3)

Reaction conditions and catalysts are not shown in these equations, andin the complete process, either reaction (1) or reaction (2) would bedone, followed by reaction (3). In these equations, only the "essential"parts of the reactants are shown. By "essential" is meant those parts ofthe reacting compounds that undergo chemical change during the process.

The (parts of) the compounds that become the trifluorovinyl ether are--O(C₂ F₄)COF and --O(C₂ F₄)C(O)O(O)C(C₂ F₄)O-- when an acyl fluoride ora carboxylic anhydride are used, respectively. By the grouping "(C₂ F₄)"is meant --CF₂ CF₂ -- or --CF(CF₃)--. The grouping --CF(CF₃)-- ispreferred. The open bonds on the one or two (in the acyl fluoride andanhydride respectively) oxygen atoms are to hydrocarbyl or substitutedhydrocarbyl groups. In addition, the acyl fluoride may have one or twoof the essential groups shown above, and the anhydride may have one ortwo anhydride groups. Thus, using either of these starting materials,trifluorovinyl ethers having one or two trifluorovinyl ether groups canbe obtained. In the case of an anhydride which has two anhydride groups,the representation above is a "formal" one, as it is possible that theanhydride may be polymeric, oligomeric or cyclic.

The following discussion of "R¹ " is applicable not only to theimmediately preceding compounds, but to all groups labeled "R¹ " herein.The group attached to the free valence of the oxygen above may bedesignated as R¹. Thus the acyl fluoride that is used can be R¹ [O(C₂F₄)COF]_(z) where z is 1 or 2 and R¹ is a hydrocarbyl or substitutedhydrocarbyl radical. By "hydrocarbyl" is meant a monovalent or divalentgroup containing only carbon and hydrogen. By "substituted hydrocarbyl"0is meant a monovalent or divalent group containing only carbon andhydrogen which contains inert substituents. By "inert" in this contextis meant that they do not change or react chemically during the process.The term "radical" herein means a group which does not change chemicallyduring a chemical reaction or process. Suitable substituents when R¹ issubstituted hydrocarbyl include, but are not limited to, fluorine, ether[between (substituted) hydrocarbyl segments], ester, sulfonyl fluoride,chloro, bromo, nitrile, sulfone [between (substituted) hydrocarbylsegments], sulfonate ester, and iodo. In one preferred embodiment all ofthe hydrogen atoms in R¹ are replaced by fluorine atoms. In anotherpreferred embodiment all of the hydrogen atoms in R¹ are replaced byfluorine atoms, and R¹ is substituted with one or more of ether, ester,or sulfonyl fluoride. In another preferred embodiment R¹ isperfluoroalkyl, pentafluorophenyl, or perfluoroalkylene. In anotherpreferred embodiment R¹ is perfluoroalkyl or perfluoroalkylenesubstituted with one or more of ether, ester, or sulfonyl fluoride.Particularly preferred R¹ groups are perfluoro-n-alkyl containing 1 to12 carbon atoms, --[CF₂ CF(CF₃)O]_(n) (CF₂)_(m) CO₂ CH₃, and --[CF₂CF(CF₃)]_(t) O(CF₂)_(m) SO₂ F wherein n is 0 or an integer of 1 to 5, tis an integer of 1 to 5 and m is 2 or 3. The starting acyl fluorides canbe made by known methods. See for example H. F. Mark, et al., Ed.,Encyclopedia of Chemical Technology, 3rd Ed., John Wiley & Sons, NewYork, 1980, Vol. 10, p. 961 and W. Gerhartz, et al., Ed., UllmannsEncyclopedia of Industrial Chemistry, 5th Ed., VCH, Weinheim, 1988, Vol.All, p. 366-367. The starting carboxylic anhydrides can be made from theacyl fluorides (see below) if desired.

Another of the needed ingredients for the process is a "siloxane". Asiloxane is a compound that contains the grouping SiOSi with each of thefree bonds to silicon bound to a hydrocarbyl, substituted hydrocarbyl,or oxysilyl group. By an oxysilyl group is meant the --OSi≡ group inwhich the free valencies of the silicon can be bound to a hydrocarbyl,substituted hydrocarbyl or additional oxysilyl groups. In this way,siloxanes containing many individual siloxane groups are built up.However, the only groups ever bound to any silicon atom (with theexception of end groups in polymers) in the siloxanes used herein, arehydrocarbyl, substituted hydrocarbyl and oxysilyl. Thus, siloxanes cancontain either one siloxane group, as in hexamethyldisiloxane, can becyclic compounds and contain several siloxane groups, as inoctamethylcyclotetrasiloxane, or can contain many siloxane groups as inpoly(dimethylsiloxane). Useful siloxanes, include, but are not limitedto, hexamethyldisiloxane, 1,3-diphenyl-1,1,3,3-tetramethyldisiloxane,hexaethyldisiloxane, 1,3-diethyl-1,1,3,3-tetramethyldisiloxane,hexamethylcyclotrisiloxane, octamethylcyclotetrasiloxane,1,3,5-triphenyl-1,3,5-trimethylcyclotrisiloxane, poly(dimethylsiloxane),poly(methyl-3,3,3-trifluoropropylsiloxane), and mixed cyclics andpolymers such as poly(dimethylsiloxane-co-phenylmethylsiloxane).Preferred siloxanes are hexamethyldisiloxane,hexamethylcyclotrisiloxane, octamethylcyclotetrasiloxane, and1,3-diethyl-1,1,3,3-tetramethyldisiloxane, and poly(dimethylsiloxane). Amore preferred siloxane is hexamethyldisiloxane.

Many siloxanes are commercially available. A short review of siloxanesis found in V. Bazant, et al., Organosilicon Compounds, vol. 1, AcademicPress, New York, 1965, p. 45-51, and references therein and T. C.Kendrick, et al., in S. Patai, et al., Ed., The Chemistry of OrganicSilicon Compounds, John Wiley & Sons, New York, 1989, Chap. 21.

In the silyl esters used and claimed herein, it is preferred if each R²and R³ is independently hydrocarbyl, more preferred if each R² and R³ isindependently phenyl or alkyl containing 1 to 4 carbon atoms, and mostpreferred if each R² and R³ is independently methyl or ethyl.

The optional catalysts for reactions (1) and (2) are compounds that aresources of the carboxylate anion --O(C₂ F₄)CO₂ ⁻. It is preferred if theoptional catalyst is present in reaction (1) and (2). The carboxylateanion itself (added as a salt) is such a source. Other sources (which inthe process can form the carboxylate anion) include but are not limitedto, silanolates, fluoride, and carboxylates such as acetate andperfluorooctanoate. In the process it is believed these compounds reactwith the acyl fluoride or carboxylic anhydride to form the carboxylatecatalyst. It is preferred if the counterion to the carboxylate catalystis an alkali metal cation. Thus, it is preferred if all of the abovecatalyst precursors are added as their alkali metal salts. Preferredcatalyst precursors (sources of catalyst) are potassium silanolates andpotassium perfluorocarboxylates.

Although not critical, it has been found useful to add 0.05 to 5 molepercent catalyst, based on equivalents of acyl fluoride present.Typically it is preferred if about 1 to 2 mole percent of the catalystor source of catalyst is used.

The thermolysis catalyst herein is an aprotic compound capable ofdesilylating a silyl ester of the formula --O(C₂ F₄)CO₂ Si≡, or a diarylsulfone. By an aprotic compound is meant a compound that does notcontain active hydrogen, such as an alcohol, phenol, carboxylic acid,and primary and secondary amine. By capable of desilylating a silylester is meant that the compound causes the silicon atom to be removedfrom the oxygen atom of at least some of the silyl ester. This can occurthrough a simple chemical reaction in which the silyl ester is convertedto another compound not having the Si--O-- bond. It also includescompounds that may cause a rapid reaction to occur in which the siliconatoms of the silyl ester molecules rapidly equilibrate with one another(i.e., the silicon atoms in effect rapidly "move" from one carboxylgroup to another). This is illustrated in Experiment 1.

Compounds capable of desilylating silyl esters (and are thereforethermolysis catalysts) include, but are not limited to, compounds whichare a source of fluoride ion, perfluorocarboxylate salts (such as --O(C₂F₄)CO₂ ⁻, but other perfluorocarboxylates are also effective),alkoxides, carboxylates, carbonates, and silanolates. In general,oxyanions and anions of carbon and sulfur acids whose conjugate acidshave a pKa of about 2 to about 32 when measured in dimethylsulfoxide(see F. G. Bordwell, Accts. Chem. Res., Vol. 21, p. 456 (1988) on howsuch measurements are made and for a list of pKas) are effectivedesilylation compounds. It is believed that the desilylation reactionsare nucleophilic attacks on silicon, which have been reviewed, see, forexample, A. R. Bassindale, et al., in S. Patai, et al., Ed., TheChemistry of Organic Silicon Compounds, John Wiley & Sons, New York,1989, Chap. 13. Preferred thermolysis catalysts are sources of fluorideion, fluorinated carboxylate salts, and silanolates. Especiallypreferred thermolysis catalysts are sources of fluoride ion,particularly an alkali metal fluoride, and most preferred is potassiumfluoride.

By a diaryl sulfone is meant a compound of the formula Ar--SO₂ --Ar,where each Ar is independently an aryl or substituted aryl group. Apreferred diaryl sulfone is diphenyl sulfone. A diaryl sulfone is notused as a thermolysis catalyst when the thermolysis is done in the gasphase.

Although not critical, it has been found useful to add 1 to 5 molepercent of the catalyst or catalyst precursor based on silyl ester, whenreaction (3) is carried out in the liquid phase. When the reaction iscarried out in the gas phase, it is preferred to have a relatively largesurface area of fluoride catalyst over which the vapor will pass.

When reaction (3) is done in the liquid phase, it is preferred to have acocatalyst present to facilitate reaction at a lower temperature. Thecocatalyst is an organic compound which is capable of complexing withthe cation of the fluoride ion source, for example the potassium ion ofKF. Suitable compounds include, but are not limited to, crown ethers,linear polyethers, sulfones, and dialkyl pyrimidones. Although notcritical, it has been found convenient to use 0.1 to 5 times theconcentration of the thermolysis catalyst, of the cocatalyst.

For reaction (1) the process temperature is not critical, but it hasbeen found convenient to use a temperature of 25° C. to 175° C.,preferably 40° C. to 125° C. Although solvents could be used in thisreaction, if desired, there is no need to do so, and it is preferred notto use solvents to avoid having to separate a solvent and product afterthe reaction. Reaction times typically range from about 0.5 to 24 hr.,usually about to 5 hr. The reactants may optionally be agitated.

If desired the product silyl ester of reaction (1) may be isolated bydistillation (assuming it has a low enough molecular weight), but thetemperature in the distillation should be kept low enough to avoidreaction (3). By a silyl ester herein is meant a compound containing thegrouping --CO₂ Si≡, and which, for example, is believed made inreactions (1) and (2), and is the starting material for reaction (3).The esters made by (1) and (2) are novel, and are useful asintermediates for the production of trifluorovinyl ethers (as inreaction (3)).

The ratio of reactants in (1), that is siloxane groups to acyl fluoridegroups, is not critical, but it is usually preferable to have an excessof siloxane groups, since this ensures complete reaction of the acylfluoride and/or anhydride and simplifies isolation of the silyl esterproduct. When using a compound containing one siloxane group (≡SiOSi≡),it is preferred if the ratio of siloxane to acyl fluoride is 4:1 to 1:1,more preferably 1.25:1 to 1.01:1. When there is more than one siloxanegroup in the siloxane compound, it is preferred if the ratio of siloxanegroups to acyl fluoride groups is 5:1 to 1.5:1, more preferably 3:1 to2:1.

It is believed that sometimes in reaction (1), anhydride (as in reaction(2)) production may precede or accompany silyl ester formation. If thathappens, anhydride may be converted to the silyl ester simply bycontinuing to heat the mixture. This is illustrated in Example 20.

Reaction (3) may be carried out in the gas or liquid phases. Asmentioned above, if done in the liquid phase, it is preferred to have acocatalyst present. If done in the liquid phase the preferredtemperature range is 140° C. to 250° C., more preferably 160° C. to 175°C. If done in the gas phase it is preferred if the temperature is 190°C. to 250° C.

Reaction (3) must be done in the liquid phase if the starting silylester is not sufficiently volatile at the process temperatures. Thiswill be more likely to occur if the silyl ester is formed from apolymeric or cyclic siloxane. When done in the liquid phase and run as abatch reaction a typical reaction time is 10 min. to 3 hr.; or thereaction may be run semi-batch (slow addition of the silyl ester to thereactor) over several hours. Agitation is optional. The reaction is mostconveniently done in the liquid phase at ambient pressure.

When reaction (3) is done in the gas phase typical contact times atelevated temperature are 10 sec. to 10 min., usually about 1 to 2 min.The reaction can be run at any convenient pressure, for example 1 Pa to5×10⁵ Pa, preferably at ambient pressure. Lower than ambient pressuresare particularly useful for relatively nonvolatile silyl esters. It ispreferred to have the catalyst for this process dispersed onto a solidsupport such as glass beads. Relatively finely divided catalyst orcatalyst precursor is preferred. The weight ratio of catalyst to silylester used is not critical, and can range from 10:1 to 0.001:1.Typically it is 0.1:1 to 0.04:1. Preferred catalysts for the gas phasethermolysis are NaF, KF and CsF.

When reaction (3) is done in either the gas or liquid phases, theprocess should be done under dry and oxygen free conditions to avoidunnecessary decomposition of the starting materials and/or products. Itis convenient to carry out the reaction under an inert gas such asnitrogen. The products of the reaction are typically purified bydistillation.

One of the products of reaction (3) is a fluorosilane. This can beconverted back to siloxane for further use in the process or for otheruses. This is done according to reaction (4):

    ≡SiF+M(OH).sub.y →≡SiOSi≡+MF.sub.y ( 4)

where y is the charge on the M cation. The metal hydroxide or anequivalent of the metal hydroxide, such as the metal or metal oxidewhich can react with water to form the hydroxide. The conversion of thefluorosilane to a tractable siloxane is more difficult when there are 3fluorine atoms on any single silicon atom, since such compounds tend toform insoluble resins. The reaction is carried out in the presence ofwater, and the hydroxide is either dissolved in, or slurried with, thewater. Preferred metal hydroxides are the alkali hydroxides, and sodium,potassium hydroxides are especially preferred. Basic metal salts arecontemplated equivalents of metal hydroxides. Alkaline earth fluorides,such as calcium fluoride, can best be made by reaction of the initiallyformed metal fluoride with CaO or Ca(OH)₂ (see Example 38). Siloxanescontaining only one siloxane group are directly formed, but if cyclic orlinear polymeric siloxanes are desired, further processing to obtainthese as "pure" compounds may be necessary (see V. Bazant et al.,supra). Thus it is preferred if the starting fluorosilane is atrihydrocarbylfluorosilane, more preferred if it is atrialkylfluorosilane in which each of the alkyl groups independently has1 to 4 carbon atoms, and especially preferred if it istrimethylfluorosilane or dimethylethylfluorosilane.

Reaction (4) is conveniently carried out at 0° C. to 100° C., preferablyabout 10° C. to 60° C. The reaction typically requires about 3-6 hr. athigher temperatures. The reaction is typically two phases, the organicand aqueous phases. These may be separated after the reaction, and theorganic phase distilled to recover relatively volatile siloxanes. The pHof the aqueous layer is preferably maintained at about 7 or morethroughout the process. The metal fluoride may be recovered byfiltration if it is insoluble in water, or the water may be evaporatedto recover soluble fluorides. The fluoride content of the metal fluoridemay be recovered as HF by treating with strong acids. Substantialamounts of CO₂ should be excluded from reaction (4).

In reaction (4), the initial ratio of hydroxyl groups of the metalhydroxide to the total number of fluorines attached to silicon ispreferably about 1:1, more preferably about 1.00:1 to 1.05:1. Largerexcesses of strong inorganic bases may lead to silanolate formationand/or foaming, both of which are undesirable. This ensures thatrelatively pure products will be produced. It is preferred to userelatively high concentrations of the metal hydroxide, for example a10-15% by weight solution of KOH, to keep the volume of the reactionlow. If the fluorosilane is relatively low boiling, it may be necessaryto do the reaction at higher than atmospheric pressure(trimethylfluorosilane boils at 18° C.).

The trifluorovinyl ethers produced by reaction (3) are useful asmonomers in free radical copolymerizations. The copolymers produced areuseful as heat and chemically resistant plastics and elastomers, see forexample H. Mark., et al., Ed., Encyclopedia of Polymer Science, JohnWiley & Sons, New York, vol. 7, 1987, p. 257-269 and vol. 16, 1989, p614-626, which are hereby included by reference. These references alsogive details of the known procedures for free radically copolymerizingtrifluorovinyl ethers. Tetrafluoroethylene is a preferred comonomer.

Tetrafluoroethylene and perfluoropropyl vinyl ether are copolymerized inaqueous . . . or nonaqueous media . . .

In aqueous copolymerization, water soluble initiators and aperfluorinated emulsifying agent are used. The tetrafluoroethylene isadded continuously to the vinyl ether. Molecular weight and molecularweight distribution are controlled by a chain transfer agent. Sometimesa second phase is added to the reaction medium to improve thedistribution of the vinyl ether in the polymer . . . ; a buffer is alsoadded.

In nonaqueous copolymerization, fluorinated acyl peroxides are used asinitiators that are soluble in the medium . . . ; a chain transfer agentmay be added for molecular weight control.

Temperatures range from 15° to 95° C., and the pressures from 0.45 to3.55 MPa. The temperatures used for the aqueous process are higher thanthose for the nonaqueous process.

Alkyl vinyl ethers tend to rearrange when exposed to free radicals . . .This could initiate a chain reaction that would result in incompleterearrangement to the isomeric acid fluoride. Temperatures must be keptlow enough to prevent termination by free-radical coupling. In theaqueous process, temperatures below 80° C. minimize the number of acidend groups derived from vinyl ether transfer. In the nonaqueous process,temperature must also be limited to avoid excessive vinyl ether transferas well as reaction with the solvent. End groups are stabilized bytreating the polymer with methanol or ammonia . . .

The polymer is separated from the medium and converted to useful formssuch as melt-extruded cubes for melt processible applications.

In the below Examples and Experiments, the following abbreviations andnames are used:

Carbowax® 1000 (Trademark, Union Carbide Corp.)--polyethylene glycol of1000 molecular weight

glyme--1,2-dimethoxyethane

(HFPO)₂ -acid fluoride--CF₃ CF₂ CF₂ OCF(CF₃)COF

Me--methyl (--CH₃)

Mn--number average molecular weight

3-n rbf--3-necked round bottom flask

PPVE--perfluoro(propyl vinyl ether)

PSEPVE--FSO₂ CF₂ CF₂ OCF(CF₃)CF₂ OCF=CF₂

TAS--tris(dimethyamino)sulfonium

THF--tetrahydrofuran

TMS--trimethylsilyl

TMSF--trimethylfluorosilane

TosOH--p-toluenesulfonic acid

It is to be understood that there is no intention to limit the inventionto the below examples but the right is reserved to all changes comingwithin the scope of the claims.

A mixture of CF₃ CF₂ CF₂ OCF(CF₃)COF (16.6 g, 50 mmol) andhexamethyldisiloxane (8.1 g, 50 mmol) was treated with potassiumtrimethylsilanolate (300 mg). After the minor exotherm subsided, themixture was heated in an oil bath at 75° C. for 3 hr. ¹⁹ F NMR showed(THF-d₈): -79.6 and -85.9 (AB pattern, OCF₂), -81.37 (t, J=9, CF₃),-82.25 (s, CF₃), -129.7 (s, CF₂), -130.2 (d, CF), -157.5 (Me₃ SiF). ¹ HNMR 0.37 (SiCH₃). Spectra are in accord with the TMS ester.

The crude ester was treated with 130 mg 18 crown-6, heated to reflux toremove remaining trimethylfluorosilane, cooled, and transferred to adropping funnel. The mixture was added dropwise to a 3-n rbf maintainedat 195° C. A slow N2 purge (ca. 30 mL/min) was used to carry volatileproducts to a collecting trap at -78° C. There was obtained 12.6 g ofcolorless liquid consisting of PPVE (34%), C₃ F₇ OCHFCF₃ (17%), and TMSF(49%) (all mole percents).

A sample of potassium trimethylsilanolate (0.5 g, 3.9 mmol) was treatedwith hexamethyldisiloxane (16.2 g, 100 mmol) and CF₃ CF₂ CF₂ OCF(CF₃)COF(34.2 g, 100 mmol). After the minor exotherm subsided, the mixture washeated in an oil bath at 60° C. for 1 hr, 75° C. for 2.5 hr, and 85° C.for 1 hr. The portion remaining in the reaction vessel was distilled togive a forerun (2.13 g; 18 weight % TMSF, 68% siloxane, 5% TMS ester)and 30.3 g of colorless liquid with bp 139°-140°. ¹⁹ F NMR (THF-d₈):-79.41 and -86.15 (AB pattern, J=152, OCF₂), -81.35 (t, J=7.1, CF₃),-82.22 (s, CF₃), -129.69 (s, CF₂), -130.35 (d, J=19, CF). An additional4.0 g of TMS ester product was obtained by vacuum transfer (at 0.1 mm).There remained 1.43 g of white solid, identified as CF₃ CF₂ CF₂OCF(CF₃)CO₂ K. ¹⁹ F NMR (THF-d₈): -81.39 and -84.18 (AB pattern, J=164,OCF₂), -81.36 (t, J=6.9, CF₃), -82.21 (s, CF₃), -126.4 (brd s, CF),-129.86 (s, CF₂).

EXAMPLE 3

The procedure of Example 2 was repeated using potassiumtrimethylsilanolate (1.5 g, 12 mmol), hexamethyldisiloxane (80.8 g, 499mmol), and CF₃ CF₂ CF₂ OCF(CF₃)COF (165.5 g, 499 mmol). Thermal programwas similar, except temperature was maintained at 85° C. for 2 hr, and111° C. for 1 hr. Distillation at ca 35 mm pressure afforded 178.5 g, bp54°-55° C. A minor amount of product appeared in the forerun, and theremaining CF₃ CF₂ CF₂ OCF(CF₃)CO₂ K was also coated with ester product.

EXAMPLE 4

A sample of potassium (HFPO)₂ acid salt obtained from Example 3 wastreated with hexamethyldisiloxane (40.0 g, 247 mmol) and CF₃ CF₂ CF₂OCF(CF₃)COF (82 g, 247 mmol). The resulting mixture was heated instages, starting at 60° C. and increasing over 4 hr to 160° C. (bathtemperature) while low-boiling by-product was collected in a gas trap.Distillation at 25-45 mm gave 88.2 g of product which was redistilled atatmospheric pressure to give 87.3 g of CF₃ CF₂ CF₂ OCF(CF₃)CO₂ SiMe₃.

EXAMPLE 5

A sample of [CF₃ CF₂ CF₂ OCF(CF₃)CO]₂ O (5.84 g, 9.1 mmol) was treatedwith hexamethyldisiloxane (1.47 g, 9.1 mmol) and heated at 100° C. for48 hr. Although the reaction was rather slow, GC analysis showed thatconversion of the anhydride to TMS ester was substantially complete(>90%) after this heating period.

EXAMPLE 6

A dry 3-n rbf was charged with diphenyl sulfone (0.20 g, 1.0 mmol) andheated at 180° C. under a slow nitrogen purge for 15 min. The reactorwas cooled and charged with CF₃ CF₂ CF₂ OCF(CF₃)CO₂ K (184 mg, 0.5 mmol)and CF₃ CF₂ CF₂ OCF(CF₃)CO₂ SiMe₃ (4.02 g, 10.0 mmol). The mixture washeated in a bath at 160° C. for 1.5 hr during which time 2.0 g ofvolatile products were collected in a gas trap. ¹⁹ F NMR analysis showedas major constituents (and wt % composition): PPVE (70%), C₃ F₇ OCHFCF₃(9.8%), TMSF (20%).

EXAMPLE 7

A dry 3-n rbf was charged with cesium fluoride (75 mg, 0.5 mmol) and CF₃CF₂ CF₂ OCF(CF₃)CO₂ SiMe₃ (4.02 g, 10 mmol) and heated in an oil bath at160° C. No observable volatiles were collected after 45 min. thereaction mixture was cooled and treated with1,3-dimethyl-3,4,5,6-tetrahydro-2(1H)-pyrimidinone (130 mg, 1.0 mmol).The mixture was heated in a bath at 160° C. to consist of PPVE (41.2mole %), TMSF (54.9%), C₃ F₇ OCHFCF₃ (3.9%), and minor unidentifiedimpurities.

EXAMPLE 8

A reactor for gas phase thermolyses was prepared as follows. A glassU-tube (1.5 cm diameter×18 cm height) was fitted at one end with anaddition port and optional supplementary inert gas supply line. Theother end of the U-tube was fitted with a ball-joint adapter leading toa series of gas trap collectors. Catalysts and solid supports were addedto the reactor under inert atmosphere, and prior to use, the system waspurged of adventitious water by heating at 225°-250° C. under acontinuous stream of nitrogen.

The above reactor was charged with a mixture of spray-dried potassiumfluoride (6 g) and glass spheres (2-3 diameter, 35 mL) and heated in abath at 225° C. CF₃ CF₂ CF₂ OCF(CF₃)CO₂ SiMe₃ (1.0 mL) was addeddropwise using a supplementary nitrogen carier flow of 30 mL/min. Therewas collected 0.75 mL (at -78° C.) of colorless liquid. ¹⁹ F NMR and GCanalysis showed a ca. 94% conversion of the TMS-ester to a mixture ofPPVE and TMSF. Only trace amounts of other components were present. Themost prominent of these was C₃ F₇ OCHFCF₃ (<1 mole %).

EXAMPLE 9

Example 8 was repeated using the same reactor and catalyst/supportcharge. CF₃ CF₂ CF₂ OCF(CF₃)CO₂ SiMe₃ (16.20 g, 40.3 mmol) was addeddropwise over 1.5 hr. There was obtained 13.94 g of liquid productconsisting of an equimolar mixture of PPVE and TMSF. Less than 0.2%starting TMS ester remained, and less than 1% C₃ F₇ OCHFCF₃ wasproduced.

EXAMPLE 10

Example 8 was repeated using the same reactor and catalyst/supportcharge. CF₃ CF₂ CF₂ OCF(CF₃)CO₂ SiMe₃ (128.6 g, 0.320 mmol) was addeddropwise at ca. 20 g/hr using N₂ carrier flow of 34 mL/min. There wasobtained 109.1 g of liquid product consisting of PPVE (49.4 mole %),TMSF (48.4%) and C₃ F₇ OCHFCF₃ (2.2%). Distillation using a 24" spinningband column gave 23.9 g of an azeotrope (74/26 TMSF/PPVE by weight),23.5 g of intermediate fractions, and 51.6 g of >99.8% purity PPVE.

EXAMPLE 11

A sample of CH₃ O₂ CCF₂ CF₂ OCF(CF₃)CF₂ OCF(CF₃)COF (52.25 g, 107 mmol)was treated with hexamethyldisiloxane (17.7 g, 109 mmol) and theresulting solution was treated with potassium trimethylsilanolate (0.5g, 3.9 mmol). After the initial exotherm subsided, the mixture washeated in stages to 80° C. at which temperature most of the expectedTMSF was collected in a trap. The temperature was increased to 100° C.for 0.5 hr and then 125° C. for 40 min to increase conversion toproducts. Distillation (0.1 mm) afforded 53.7 g of colorless liquid, bp63° C. ¹⁹ F NMR (THF-d₈ /F11): -79.0 and -84.1 (overlapping AB patterns,J=141, OCF₂), -79.91 (m, CF₃), -82.13 and -82.16 (singlets, CF₃ 's fortwo diastereomers), -82.9 (m, OCF₂), -121.17 and -121.24 (equallyintense triplets, J=2.9, CF₂, -130.05 (apparent t, J=18, CF), -144.9 (t,J=22, CF). ¹ H NMR 3.93 (s, OCH₃), 0.39 (s, SiCH₃).

EXAMPLE 12

Gas phase thermolysis was carried out using a reactor containingspray-dried KF and glass beads (described in Example 8) modified toaccommodate a glass side-arm and distillation flask on the feed side.The U-tube reactor was maintained at 225°-230° C. during the reaction. Asample of MeO₂ CCF₂ CF₂ OCF(CF₃)CF₂ OCF(CF₃)CO₂ SiMe₃ (4.6 g, 8.4 mmol)was slowly added from the distillation flask by reducing the pressure to0.05 mm and heating the flask in a separate bath at ca. 70° C. Productswere collected in a gas trap cooled at -78° C. There was obtained 2.66 gof colorless liquid consisting of a mixture of Me₃ SiF and CF₂ =CFOCF₂CF(CF₃)OCF₂ CF₂ CO₂ Me as shown by comparison with authentic samples(GC) and ¹⁹ F NMR (THF-d₈ /F₁₁): -79.9 (m, CF₃), -82.9 and -84.6(centers of OCF₂ m's), -113.7 (dd, J=65, 85, CF), -121.3 (m, CF₂),-121.7 (dd of t's, J=85, 112, 6, CF), -136.65 (dd of t's, J=65, 112, 6,CF), -144.9 (t, J=21.6, CF), -157.5 (m, SiF).

EXAMPLE 13

A sample of FSO2CF₂ CF₂ OCF(CF₃)COF (35.2 g, 101 mmol) was treated withhexamethyldisiloxane (16.4 g, 101 mmol) and potassiumtrimethylsilanolate (0.38 g, 3 mmol) at 25° C. The mixture was heated instages from 50° C. to 97° C., and the temperature was maintained at 97°C. for 1.5 hr. Distillation at 0.2 mm gave a small forerun and 35.2 g ofcolorless oil with bp =28° C. ¹⁹ F NMR (THF-d₈): +45.30 (apparentpentet, J=5.7, FSO₂), -81.92 (s, CF₃), -77.24 and -83.59 (AB pattern,J=147, with lower-field portion exhibiting additional J=18.5), -112.08(s, CF₂), -130.16 (d, J=18.2, CF), in accord with FSO₂ CF₂ CF₂OCF(CF₃)CO₂ SiMe₃.

EXAMPLE 14

A mixture of FSO2CF₂ CF₂ OCF(CF₃)CF₂ OCF(CF₃)COF (7.14 g, 13.9 mmol) andhexamethyldisiloxane (2.26 g, 13.9 mmol) was treated with potassiumtrimethylsilanolate (64 mg, 0.5 mmol) and heated at 60° C. for 0.5 hr,80° C. for 0.5 hr, and 125° C. for 1.5 hr. Distillation at 0.05 mm gavea forerun (0.8 g) and the major fraction (4.9 g) at 42°-43° C. Some ofthe desired product remained in the distillation pot along with thecorresponding potassium carboxylate. ¹⁹ F NMR (THF-d₈): +45.4 (m, FSO2),-77.8 to -80.0 (overlapping lower-field OCF₂ AB and CF₃), -82.11 and-82.15 (singlets, CF₃), -84.0 (high-field portion of AB pattern, J=140,OCF₂), -111.9 (m, CF₂), - 130.0 (m, CF), -144.4 (overlapping m's, CF). ¹H NMR 0.38 (s). Spectra are in accord with FSO₂ CF₂ CF₂ OCF(CF₃)CF₂OCF(CF₃)CO₂ SiMe₃.

EXAMPLE 15

A sample of FSO₂ CF₂ CF₂ OCF(CF₃)CF₂ OCF(CF₃)CO₂ SiMe₃ (4.8 g, 8.2 mmol)was added dropwise over 1 hr to the U-tube reactor (described in Example8) containing KF glass beads at 220°-230° C. There was obtained 4.07 gof colorless liquid consisting of a ca. 1/1 mixture of PSEPVE and TMSF.¹⁹ F NMR (THF-d₈): +45.3 (m, FSO₂), -79.1 (m, CF₂), -79.9 (m, CF₃),-84.5 (m, CF₂), -112.1 (m, SO₂ CF₂), -113.2 (dd, J=66, 84, CF), -121.41(dd of t's, J=84, 112, CF), -136.45 (dd of t's, J=66, 112, 6, CF),-157.7 (m, FSiMe₃).

EXAMPLE 16

A mixture of CF₃ CF₂ CF₂ OCF(CF₃)COF (6.0 g, 18 mmol) and cesiumfluoride (200 mg, 1.3 mmol) was treated with hexamethylcyclotrisiloxane(1.5 g, 6.8 mmol). The mixture was then treated with TAS Me₃ SiF₂ (50mg) and allowed to stand for two days. The mixture was heated in an oilbath at 130°-150° C. to provide 2.2 g of colorless liquid. ¹⁹ F NMRanalysis showed two major products, PPVE and C₃ F₇ OCHFCF₃ in a ca.73/27 ratio.

EXAMPLE 17

A mixture of CF₃ CF₂ CF₂ OCF(CF₃)COF (16.6 g, 50 mmol) andhexamethylcyclotrisiloxane (4.1 g, 18.5 mmol) was treated with potassiumsilanolate (300 mg, 2.3 mmol). After the exotherm subsided, thehomogeneous solution was heated to 160° C. (internal temperature) while3.0 mL of colorless liquid was collected in a gas trap. Bulk of thisvolatile portion was dimethyldifluorosilane; a minor amount of unreacted(HFPO)₂ acid fluoride was also collected. The mixture was cooled to 25°C. and 18-crown-6 (80 mg, 0.3 mmol) was added. The mixture was heated to150° C., then 175°-180° C., at which temperature 11.2 mL of colorlessliquid was collected. ¹⁹ F NMR (THF-d₈) showed -81.84 (t, J=7.4, CF₃),-86.35 (m, CF₂ O), -114.0 (dd, J=66, 85, vinyl CF), -122.1 (dd oftriplets, J= 85, 112, 5.7, vinyl CF), -129.96 (s, CF₂), -135.94 (dd oftriplets, J=66, 112, 5.8, vinyl CF), -147.2 (d of m's, J=51, CHF),consistent with a ca 95/5 ratio of PPVE/C₃ F₇ OCHFCF₃). Small amounts offluorine-ended dimethylsiloxane oligomers (predominantly Me₂ FSiOSiMe₂F) were present, as evidenced by septets at -131.9 and -131.15.

EXAMPLE 18

A 4.04 g sample of trimethylsilyl-terminated dimethylsiloxane polymer(mol. wt.=9430) was treated with potassium fluoride (100 mg), potassiumtrimethylsilanoate (300 mg), and Carbowax® 1000 (80 mg) and heated at125° C. for 15 min. The mixture was cooled to 25° C. and treated withCF₃ CF₂ CF₂ OCF(CF₃)COF (17.0 g, 51 mmol). The mixture was heatedgradually in an oil bath from 50° C. to ca. 190° C., collecting 10.05 gof volatile products in a gas trap at -78° C. ¹⁹ F NMR analysis showed amixture of PVE (75 mole %), C₃ F₇ OCHFCF₃ (11%), and (HFPO)₂ -acidfluoride (5%). There remained 3.00 g of by-product ketone [C₃ F₇OCF(CF₃)]₂ CO in the pot.

EXAMPLE 19

A mixture of CF₃ CF₂ CF₂ OCF(CF₃)COF (7.54 g, 22.7 mmol) andhexamethylcyclotrisiloxane (1.68 g, 7.6 mmol) was treated with potassiumtrimethylsilanolate (80 mg, 0.63 mmol). After the mild exotherm subsidedand solid trisiloxane had disappeared, the reaction mixture was stirredfor an additional 0.5 hr. Volatiles were transferred under vacuum (0.1mm) to give 7.45 g of colorless liquid. Storage at -25° C. provided 6.1g (84% yield) of a lower layer. ¹⁹ F NMR (THF-d₈) featured two ABpatterns -79.80 and -86.15 (J=160), and -79.80 and -86.30 (J=160, OCF₂),-81.8 (t) and -81.95 (s, CF₃ 's), -129.98 (s, CF₂), -131.98 (d, J=19.6,CF). IR featured C=O bands at 1868 and 1802 cm⁻¹. Spectral data are inaccord with the anhydride: [CF₃ CF₂ CF₂ OCF(CF₃)CO]₂ O.

EXAMPLE 20

A mixture of CF₃ CF₂ CF₂ OCF(CF₃)COF (15.7 g, 47.3 mmol) andoctamethylcyclotetrasiloxane (14.0 g, 47.2 mmol) was treated withpotassium trimethylsilanolate (256 mg, 2.0 mmol) and stirred at ambienttemperature for 1.2 hr. GC and ¹⁹ F NMR analyses of an aliquot showedthat starting acid fluoride and the anhydride characterized in Example19 were the predominant fluorocarbon species present. The mixture wasthen heated at 75° C., and the temperature was gradually increased to186° C. over 3 hr. GC analysis showed that acid fluoride and theanhydride had been nearly completely consumed. ¹ H NMR showed SiCH₃signals at 0.404 and 0.396 (characteristic of RfCO₂ SiMe₂) as well asSiCH₃ at 0.15-0.09. ¹⁹ F NMR was likewise consistent with a mixture ofdimethyl(perfluoroalkylcarboxy)-terminated and dimethylfluoro-terminateddimethylsiloxane oligomers. GC/MS analysis of these intermediates in asimilar experiment provided good evidence for the formation ofintermediate silyl esters. For example, the observed m/z of 538.999878had the elemental composition of C₁₁ H₁₅ O₅ Si₃ F₁₂(calc'd.=539.0035726) and is assigned to [C₃ F₇ OCF(CF₃)CO₂ SiMe₂ OSiMe₂OSiMe₂ F--Me]. Similarly, observed m/z=613.005127 had the elementalcomposition [C₃ H₂₁ F₁₂ O₆ Si₄ (calc'd.=613.0223659) and is assigned to[C₃ F₇ OCF(CF₃)CO₂ SiMe₂ O(SiMe₂ O)₂ SiMe₂ F--Me]. The mixture wascooled to 25° C., and 18-crown-6 (132 mg, 0.5 mmol) was added. Uponheating at 160°-185° C. (bath temperature), 8.5 mL (11.4 g) of colorlessvolatiles were collected in a gas trap. ¹⁹ F NMR analysis showed this toconsist of PPVE (80 mole %), C₃ F₇ OCHFCF₃ (10%), and Me₂ SiFOSiMe₂ F(9%). There remained after thermolysis 12.6 g of liquid and a smallamount of insoluble material. NMR and GC/MS showed the liquid consistedof dimethylfluoro-terminated dimethylsiloxane oligomers (Me₂ FSiO(Me₂SiO)_(n) SiMe₂ F, n=0 to 13) along with a small amount of cyclic trimer,tetramer, and pentamer (D₃ to D₅). For example (n=3), observedm/z=377.067902; calc'd. m/z=377.0723831 for C₉ H₂₇ F₂ O₄ Si₅ (M-CH₃).

EXAMPLE 21

Example 20 was repeated using CF₃ CF₂ CF₂ OCF(CF₃)COF (17.2 g, 51.8mmol), freshly distilled octamethylcyclotetrasiloxane (7.7 g, 26 mmol),and potassium trimethylsilanolate (256 mg, 2.0 mmol). 18-Crown-6 (130mg) was added after GC analysis showed substantial consumption of theintermediate anhydride. Prior to liberation of PPVE, there was collected1.11 g of volatiles consisting (mol %) of Me₂ SiF₂ (52), C₃ F₇ OCHFCF₃(13), Me₃ SiF (14), and (HFPO)₂ -acid fluoride (21). Thermolysis in thepresence of 18-crown-6 gave 12.1 g of condensate consisting (wt %) ofPPVE (81), C₃ F₇ OCHFCF₃ (7), Me₂ SiFOSiMe₂ F (7.6), and Me₂ SiF₂ (5).Yield of PPVE was thus ca. 75%.

EXAMPLE 22

A 3-n rbf fitted with reflux condenser, internal liquid and vaportemperature sensors, was connected to a gas trap for the collection oflower boiling components. The flask was charged with CF₃ CF₂ CF₂OCF(CF₃)COF (17.2 g, 52 mmol) and octamethylcyclotetrasiloxane (8.0 g,27 mmol) and then potassium trimethylsilanolate (256 mg, 2 mmol). Afterthe exotherm subsided, the mixture was heated in stages to 150° C.(internal temperature ca. 135° C.) over a period of 5.5 hr. Collectionof volatiles began when the internal temperature reached ca. 70° C., butonly 1.8 mL of volatiles was obtained. The major part of this trapliquid was Me₂ SiF₂, minor components included (HFPO)₂ -acid fluorideand C₃ F₇ OCHFCF₃. The pot residue was treated with 18-crown-6 (130 mg,0.5 mmol) and heated at 150° C. There was obtained 12.1 g of liquid inthe trap after warming to 15° C. ¹⁹ F NMR showed (mol %) the followingspecies: PPVE (72.0), C₃ F₇ OCHFCF₃ (5.9), Me₂ FSiOSiMe₂ F (10.6), Me₂SiF₂ (11.7). The pot residue was processed to provide 5.8 g of oil shownby NMR and GC/MS to consist of a series of fluorine-terminateddimethylsiloxane oligomers containing from 2 to 14 silicon atoms.

EXAMPLE 23

A 3-n rbf fitted with reflux condenser, internal liquid and vaportemperature sensors, was connected to a gas trap for the collection oflower boiling components. The flask was charged with CF₃ CF₂ CF₂OCF(CF₃)COF (16.5 g, 9.7 mmol) and octamethylcyclotetrasiloxane (7.4 g,4.8 mmol) and potassium trimethylsilanolate (256 mg, 2 mmol). After theexotherm subsided, the mixture was heated in stages to 150° C. (internaltemperature ca. 135° C.) over a period of 2.5 hr. Collection ofvolatiles began when the internal temperature reached ca. 70° C., butonly 1.25 mL of volatiles was obtained. The major part of this trapliquid was Me₂ SiF₂, minor components included (HFPO)₂ -acid fluorideand C₃ F₇ OCHFCF₃. The pot residue was then heated at 150°-200° C. forca. 7 hr. There was obtained 14.3 g of liquid in the trap. From theweight and composition (determined by GC and NMR) the yield of PPVE wasdetermined as 74%. C₃ F₇ OCHFCF₃ was the most prominent by-product, andthe ketone [C₃ F₇ OCF(CF₃)]₂ CO was a minor one. Me₂ FSiOSiMe₂ F and Me₂SiF₂ were the volatile fluorosilanes present in the trap. The potresidue was comparable to previous examples and consisted of a series offluorine-terminated dimethylsiloxane oligomers containing from 2 to 14silicon atoms.

EXAMPLE 24

A 3-n rbf fitted with reflux condenser, internal liquid and vaportemperature sensors, was connected to a gas trap for the collection oflower boiling components. The flask was charged with CF₃ CF₂ CF₂OCF(CF₃)COF (15.3 g, 46 mmol) and cesium fluoride (200 mg, 1.3 mmol).Hexamethylcyclotrisiloxane (3.8 g, 17.1 mmol) was added in one portion.After the solid dissolved and the exotherm subsided, the mixture washeated in stages to 175° C. Collection of volatiles began when theinternal temperature reached ca. 120° C. There was obtained 7.5 mL (at-78° C.) of liquid in the trap after ca. 4 hr. Volatile product wasfractionated by warming to -50, -30, 0, and then 15° C. to removetrapped CO₂ and the bulk of dimethyldifluorosilane. ¹⁹ F NMR of theremaining 7.45 g (5.8 mL) of volatile product showed PPVE, C₃ F₇ CHFCF₃,and (HFPO)₂ -acid fluoride in a 73/13/13 ratio. Continued thermolysis ofthe pot residue produced a small amount (1.0 mL, 1.52 g) of additionalpyrolysate which was predominantly PPVE by ¹⁹ F NMR analysis.

EXAMPLE 25

A 3-n rbf fitted with reflux condenser, internal liquid and vaportemperature sensors, was connected to a gas trap for the collection oflower boiling components. The flask was charged with CF₃ CF₂ CF₂OCF(CF₃)COF (16.6 g, 50 mmol) and hexamethylcyclotrisiloxane (4.1 g,18.5 mmol) and then potassium trimethylsilanolate (300 mg, 2.3 mmol).After the solid dissolved and the exotherm subsided, the mixture washeated in stages to 180° C. (internal temperature ca. 160° C.) over aperiod of 1.0 hr. Collection of volatiles began when the internaltemperature reached ca. 100° C., but only 3.0 mL of volatiles wasobtained. The major part of trap liquid was Me₂ SiF₂, minor componentsincluded (HFPO)₂ -acid fluoride and C₃ F₇ OCHFCF₃. After standing for 18hr, the pot residue was treated with 18-crown-6 (80 mg, 0.3 mmol) andheated at 175°-180° C. There was obtained 11.5 mL (at -78° C.) of liquidin the trap after ca. 1 hr. Volatile product was fractionated by warmingto -50, -30, 0, and then 15° C. to give 11.2 mL of liquid. ¹⁹ F NMR(THF-d₈ /F₁₁): -81.84 (t, J=7.4, CF₃), -86.35 (m, OCF₂), -114.00 (dd,J=66, 85, vinyl CF), -122.10 (dd of t's, J_(t) =5.7, J_(d) =85, 112),-129.96 (s, CF₂), -135.94 (dd of t's, J_(t) =5.8, J_(d) =66, 112, vinylCF); minor signals at -130.18, -131.15, and -131.9 due to FMe₂ Si-fragments; and d of m's at -147.2 characteristic of C₃ F₇ OCHFCF₃. PPVEpurity was estimated as about 95%.

EXAMPLE 26

A 3-n rbf fitted with reflux condenser, internal liquid and vaportemperature sensors, was connected to a gas trap for the collection oflower boiling components. The flask was charged with TMS-terminatedpolydimethylsiloxane (4.04 g, 3.82 mL, mol wt. ca. 9400), potassiumfluoride (100 mg), potassium trimethylsilanolate (300 mg), and Carbowax®1000 (80 mg). The mixture was heated at 125° C. for 20 min, cooled to25° C. and treated with CF₃ CF₂ CF₂ OCF(CF₃)COF (17.0 g, 51 mmol). Themixture was heated gradually and in stages to 190° C. (bath temperature)over a period of 4.0 hr. Collection of volatiles began when the internaltemperature reached ca. 70° C. There was obtained 8.5 mL (10.1 g) afterwarming the volatile fraction to 15° C. ¹⁹ F NMR analysis showed thisproduct consisted of a mixture of PPVE (75%), C₃ F₇ OCHFCF₃) (11%),(HFPO)₂ (5%), and a minor quantity of unidentified material. Thefluorocarbon fraction (3.0 g) obtained from the pot residue consistedmainly of a mixture of diastereomeric ketones of the structure [C₃ F₇OCF(CF₃)]₂ CO.

EXAMPLE 27

A mixture of [CF₃ CF₂ CF₂ OCF(CF₃)CO]₂ O (2.57 g, 4.0 mmol) andhexamethyldisiloxane (648 mg, 4.0 mmol) in a sealed glass vial washeated in a bath at 100° C. The (initially) two-phase mixture wasstirred vigorously using a small magnetic stir bar. Composition of themixture was determined by GC analysis using authentic standards.Approximate composition (anhydride/siloxane/CF₃ CF₂ CF₂ OCF(CF₃)CO₂SiMe₃) varied with time as follows:

    ______________________________________                                        18 hr                60/30/10                                                 42 hr                40/20/36                                                 96 hr                25/11/64                                                 120 hr               20/8/73                                                  ______________________________________                                    

EXAMPLE 28

A mixture of [CF₃ CF₂ CF₂ OCF(CF₃)CO]₂ O (2.57 g, 4.0 mmol) andhexamethyldisiloxane (648 mg, 4.0 mmol) was treated with CF₃ CF₂ CF₂OCF(CF₃)CO₂ K (29 mg, 0.08 mmol) in a sealed glass vial. The reactionmixture was heated in a bath at 100° C. The (initially) two-phasemixture was stirred vigorously using a small magnetic stir bar.Composition of the mixture was determined by GC analysis using authenticstandards. Approximate composition (anhydride/siloxane/CF₃ CF₂ CF₂OCF(CF₃)CO₂ SiMe₃) varied with time as follows:

    ______________________________________                                               3.5 hr            52/23/25                                                    18  hr            31/4/65                                                     42  hr            15/2.5/83                                                   96  hr            9/0/91                                               ______________________________________                                    

EXAMPLE 29

A mixture of [CF₃ CF₂ CF₂ OCF(CF₃)CO]₂ O (2.57 g, 4.0 mmol) andhexamethyldisiloxane (648 mg, 4.0 mmol) was treated with Me₃ SiOK (10mg, 0.08 mmol) in a sealed glass vial. The reaction mixture was heatedin a bath at 100° C. The (initially) two-phase mixture was stirredvigorously using a small magnetic stir bar. Composition of the mixturewas determined by GC analysis using authentic standards. Approximatecomposition (anhydride/siloxane/CF₃ CF₂ CF₂ OCF(CF₃)CO₂ SiMe₃) variedwith time as follows:

    ______________________________________                                               40  min          35/18/47                                                     70  min          24/18/58                                                     40  hr           1.3/1.6/97.0                                                 94  hr           0.9/1.4/97.7                                          ______________________________________                                    

EXAMPLE 30

A sample of fluorine-ended dimethylsiloxane oligomers (2.00 g, est.Mn=400, 5 mmol) obtained from the reaction of (HFPO)₂ -acid fluoride andoctamethylcyclotetrasiloxane was treated with calcium carbonate (0.5 g)and calcium oxide (0.25 g) and heated for 1.5 hr at 150° C., then 0.75hr at 200° C. without change in composition. The sample was then treatedwith Ca(OH)₂ (0.3 g) and heated at 200° C. for 40 min. GC analysis ofthe crude mixture showed a low conversion to the cyclic trimer, tetramer(D₄), and pentamer (D₅) of dimethylsiloxane.

EXAMPLE 31

A sample of fluorine-ended dimethylsiloxane oligomers obtained as inExample 30 (5.0 g) was treated with Ca(OH)₂ (0.75 g) and heated at 220°C. for 0.5 hr. The pressure was then reduced to 0.1 mm and 0.45 g ofdistillate was obtained which consisted mainly of D₃, D₄, and D₅. Themixture was cooled to 25° C. and treated with 75 mg KOH and again heatedat 220° C./0.1 mm to provide 2.70 g of a mixture of D₃ -D₉. Structureswere confirmed by GC/MS.

EXAMPLE 32

A mixture of fluorine-ended dimethylsiloxane oligomers obtained as inExample 30 (5.24 g), calcium hydroxide (0.9 g), potassium hydroxide (75mg), and glyme (25 mL) was heated at reflux for 3 hr. Solid was removedby filtration, and the filtrate was treated with water (50 mL). The toplayer was dissolved in methylene chloride and washed several times withwater, dried, and stripped to give 4.74 g of light yellow oil. Kugelrohrdistillation afforded 1.95 g of colorless oil, consisting mainly of D₄and D₅ but containing also D₆ -D₁₂. The pot residue was treated with 50mg KOH and heated under vacuum (150° C., 0.5 mm). The volatiles fromthis fraction (2.40 g) consisted of D₃ -D₇ with very small amounts of D₈and D₉.

EXAMPLE 33

A mixture of fluorine-ended dimethylsiloxane oligomers obtained as inExample 30 (8.12 g, Mn ca. 3000), calcium hydroxide (0.2 g), potassiumhydroxide (50 mg), and glyme (35 mL) was heated at reflux for 3 hr. Themixture was filtered, stripped, dissolved in CH₂ Cl₂, washed with water,dried and stripped. The resulting light yellow oil was treated with KOH(25 mg) and heated in an oil bath at 170° C. (0.2 mm) to provide 8.55 gof colorless distillate consisting of 8.00 g of D₃ -D₇ and ca. 0.5 gresidual solvent. Yield of cyclic oligomers was thus >98%.

EXAMPLE 34

A glass vial of 20 mL capacity (cleaned by rinsing consecutively withdistilled water, acetone, THF; dried at 115° C. for 24 hr and stored inan atmosphere of dry nitrogen) was charged with CF₃ CF₂ CF₂ OCF(CF₃)COF(332 mg, 1.0 mmol) and hexamethyldisiloxane (162 mg, 1.0 mmol) andsealed using a polypropylene screw cap. The vial was heated in a sandbath maintained at 100° C. The reaction was monitored by GC analysis.The vial was cooled to -25° C., then warmed sufficiently to obtain asingle liquid phase of reactants and products. After 20 hr under theseconditions, two fluorocarbon-containing components were present: CF₃ CF₂CF₂ OCF(CF₃)COF 44 hr, the composition consisted of acid fluoride(18.6%), anhydride (2.3%), and silyl ester (79.1%).

EXAMPLE 35

A glass vial of 20 mL capacity (cleaned by rinsing consecutively withdistilled water, acetone, THF; dried at 115° C. for 24 hr and stored inan atmosphere of dry nitrogen) was charged with CF₃ CF₂ CF₂ OCF(CF₃)COF(498 mg, 1.5 mmol) and 1,1,2,2-tetramethyl-1,3-diethyldisiloxane (285mg, 1.5 mmol) and a small teflon-coated stir bar and sealed using apolypropylene screw cap. The vial was heated in a sand bath maintainedat 100° C. The reaction was monitored by GC analysis. The vial wascooled to -20° C., then warmed sufficiently to obtain a single liquidphase of reactants and products (ca. 0° C.). After 13 hr under thesepresent: CF₃ CF₂ CF₂ OCF(CF₃)COF (83 mole %) and CF₃ CF₂ CF₂ OCF(CF₃)CO₂SiMe₂ Et (17%). After 37 hr, the composition consisted of acid fluoride(51.9%), anhydride (2.8%), and silyl ester (45.3%).

EXAMPLE 36

A 3-n rbf was charged with calcium hydroxide (1.59 g, 21.5 mmol),potassium hydroxide (25 mg), and water (30 mL). The mixture was cooledto 0° C. and treated with trimethylfluorosilane (5.0 mL at 0° C., 4.0 g,43 mmol). After addition was complete, the temperature was allowed toincrease to 20° C. The mixture was heated to 50° C., and the refluxcondenser was replaced with a still head. Product hexamethyldisiloxaneand trimthylsilanol was collected in the lower-boiling fraction whichbegan at ca. 77° C. Separation of the two liquid layers in thedistillate provided 2.45 g of organic material which consisted oftrimethylsilanol (28%) and hexamethyldisiloxane (68%). Addition of atrace amount of toluenesulfonic acid facilitated the condensation oftrimethylsilanol, and resulted in hexamethyldisoloxane of >99% purity.Solid remaining in the distillation pot was filtered and dried to give1.75 g of white solid.

EXAMPLE 37

A solution of calcium acetate hydrate (16.9 g, 95.9 mmol) in water (50mL) at 2°-4° C. was treated with trimethylfluorosilane (8.83 g, 96mmol). The vessel was sealed and allowed to warm to 25° C. over 2 hr.Distillation at atmospheric pressure afforded 6.64 g of colorless liquidwhich consisted of TMSF (2.5%), TMSOH (2.4%), and (TMS)₂ O (95.2%). Thepot residue was treated with an antifoaming agent, Dow Corning DB-31,and again subjected to distillation to provide an additional 0.5 g ofhexamethyldisiloxane. The remaining solid was filtered and dried to give5.95 g of material. Elemental analysis confirmed that acetate waspresent in this product.

EXAMPLE 38

A solution of KOH (86.2 mequiv.) in water (35 mL) was prepared in a 70mL Fisher-Porter bottle and cooled to 0° C. Trimethylfluorosilane (10.0mL, 7.93 g) was added, and the vessel was sealed. The mixture was warmedto 25° C. and stirred for 1.75 hr. The vessel was pressurized with N₂(at 7 psi) and heated at 35° C. for 0.5 hr. The mixture was cooled to 0°C. and the top layer was analyzed by GC: 0.1% H₂ O, 6.6% Me₃ SiOH, 93.3%Me₃ SiOSiMe₃. Layers were separated, and the bottom layer was subjectedto distillation to remove a small amount of siloxane. Obtained a totalof 6.32 g (90.5% recovery) hexamethyldisiloxane after treating theproduct with a trace of TsOH. The aqueous layer was treated with calciumhydroxide (3.19 g, 43.1 mmol), stirred for 18 hr, and filtered. Thebasic filtrate was used as reagent for another charge oftrimethylfluorosilane as described above. The reaction was monitored byGC. When the composition remained constant (ca. 6% TMSF), an additionalcharge of KOH (0.335 g) was added and the pressurized mixture wasstirred for 18 hr at 45° C. The quantity of isolatedhexamethyldisiloxane was 6.11 g.

EXAMPLE 39

A 3-n rbf fitted with a reflux condenser and a N₂ purge inlet wascharged with diphenyl sulfone (0.6 g, 2.75 mmol). CF₃ CF₂ CF₂OCF(CF₃)CO₂ SiMe₃ (4.02 g, 10 mmol) was added in one portion. Themixture was heated in an oil bath at 160° C. There was obtained 1.4 mL(@ 0° C.) after 1.5 hr. ¹⁹ F NMR features PPVE and TMSF as majorproducts, although the PPVE/C₃ F₇ OCHFCF₃ ratio was 65/35. A number ofunidentified byproducts were also present.

EXAMPLE 40

A mixture of CF₃ CF₂ CF₂ OCF(CF₃)CO₂ SiMe₃ (4.0 g), Cs₂ CO₃ (50 mg), anddiphenyl suflone (100 mg) was placed in a 3-n rbf (fitted with a refluxcondenser and connected to a gas trap) and heated in an oil bath at 170°C. There was obtained 2.44 g of colorless volatiles which consisted of a44.4/1.2/54.4 (mol %) mixture of PPVE/C₃ F₇ CHFCF₃ /TMSF by ¹⁹ F NMR. GCanalysis showed two peaks with an area ratio 67.7/32.3 (PPVE/TMSF).

EXAMPLE 41

Fluorine chemical shifts are reported in ppm from CFCl₃. Spectra wererecorded on a Nicolet NT200 spectrometer at 188.2 MHz. Solvents withminimum water concentrations are required for reliable results in theNMR experiments described herein. Ether and THF were distilled fromsodium-benzophenone and then stored over activated sieves. All reactionswere carried out in an atmosphere of dry nitrogen, and manipulations andsample preparations were carried out in a Vacuum Atmospheres drybox.Typical substrate concentrations were ca. 0.1 to 0.2M.

The spectrum of the mixture of CF₃ CF₂ CF₂ OCF(CF₃)CO₂ K (92 mg, 0.25mmol) and CF₃ CF₂ CF₂ OCF(CF₃)CO₂ SiMe₃ (100 mg, 0.25 mmol) in THF-d₈showed a single set of signals for the fluorocarbon framework: -80.53and -85.12 (AB pattern, J=142 Hz, OCF₂), -81.39 (t, J=7.2 Hz, CF₃)-82.24 (d, J=1.9 Hz, CF₃), -128.2 (bd s, CF), -129.82 (s, CF₂). Thisspectrum exhibits simple averaged shifts for the corresponding segmentsof the two components. Spectral parameters for the separate componentsare given for comparison: [R_(f) CO₂ K: -81.7 and -84.0 (AB pattern),-81.33 (t, J=7.2), -82.2 (d, J=2.3), -125.6 (m, CF), -129.9 (s); R_(f)CO₂ SiMe₃ : -79.41 and -86.18 (AB pattern, J=152), -81.37 (t, J=7.1),-82.24 (d, J=1.5), -129.71 (s), and -130.38 (d, J=18.9); R_(f) CO₂ TAS:-81.3 and -83.2 (AB pattern, J=146), -81.22 (t, J=6.8), -81.40 (d,J=1.7), -122.9 (m), -129.76 (s).]

For simplest analysis in other reactions reported here, examination ofthe shift for the CF group is the most informative. The spectrum of asimilar mixture, prepared by reaction of the anhydride and oneequivalent of potassium trimethyl silanolate, was temperature-invariantto -80° C., demonstrating the facility of the trimethylsilyl exchangeprocess.

Chemical shifts of the CF resonance for representative mixtures of CF₃CF₂ CF₂ OCF(CF₃)CO₂ SiMe₃ /desilylation reagent (1.00/0.20 mol ratio)are given in the table below. In all these cases, the "desilyationreagent" is only slightly soluble in THF-d₈, but dissolves and reactsupon addition of the TMS ester. Shifts for the R_(f) CO₂ ⁻ are dependentupon counterion.

    ______________________________________                                        desilylation reagent                                                                             chem. shift of CF                                          ______________________________________                                        Et4N.sup.+ CN.sup.-                                                                              -128.8                                                     CF.sub.3 CO.sub.2 K                                                                              -129.4                                                     TAS d-10-camphorsulfinate                                                                        -129.04 [TAS = tris(di-                                                       methylamino)sulfonium]                                     ______________________________________                                    

A short discussion of the effects of chemical exchange on NMR spectramay be found in R. K. Harris, "Nuclear Magnetic ResonsanceSpectroscopy", Pittman Publishing Inc., 1983, Chap. 5.

What is claimed is:
 1. A process for the production of trifluorovinylethers, comprising:(a) reacting a siloxane with a compound of theformula R¹ [O(C₂ F₄)COF]_(z) or a compound of the formula R¹ [O(C₂F₄)C(O)O(O)C(C₂ F₂)O]_(z) R¹ wherein z is 1 or 2 and R¹ is a hydrocarbylor substituted hydrocarbyl radical having z free valencies, and whereinthe substituent is inert under process conditions; (b) heating in thepresence of a thermolysis catalyst at a temperature of about 140° C. toabout 350° C., to produce a trifluorovinyl ether and a fluorosilane,provided that when (b) is done in the gas phase, said thermolysiscatalyst is not a diaryl sulfone.
 2. The process as recited in claim 1wherein (a) is done in the presence of a first catalyst which underprocess conditions is capable of generating a compound which contains acarboxylate anion grouping --O(C₂ F₄)CO₂ ⁻.
 3. The process as recited inclaim 1 wherein said compound in step (a) is R¹ [O(C₂ F₄)COF]_(z). 4.The process as recited in claim 3 wherein said R¹ is substituted withone or more of fluorine, ether, ester, sulfonyl fluoride, chloro, bromo,iodo, nitrile, sulfone, or sulfonate ester.
 5. The process as recited inclaim 3 when said R¹ is alkyl or alkylene.
 6. The process as recited inclaim 5 wherein all hydrogen atoms in said R¹ are replaced by fluorineatoms.
 7. The process as recited in claim 6 wherein said R¹ issubstituted with one or more of ether, ester or sulfonyl fluoride. 8.The process as recited in claim 3 wherein said z is 1 and said R¹ isperfluoro-n-alkyl containing 1 to 12 carbon atoms, --[CF₂ CF(CF₃)O]_(n)(CF₂)_(m) CO₂ CH₃, or --[CF₂ CF(CF₃)O]_(t) (CF₂)_(m) SO₂ F, wherein n is0 or an integer of 1 to 5, t is an integer of 1 to 5, and m is 2 or 3.9. The process as recited in claim 1, 2, 3, 4, 5, 6, 7, or 8 whereinsaid siloxane is hexamethyl-disiloxane, hexamethylcyclotrisiloxane,octamethylcyclotetrasiloxane, 1,3-diethyl-1,1,3,3-tetramethyldisiloxane,or poly(dimethylsiloxane).
 10. The process as recited in claim 9 whereinsaid siloxane is hexamethyldisiloxane.
 11. The process as recited inclaim 1, 2, 3, 4, 5, 6, 7, or 8 in which said first catalyst is asilanolate, fluoride or carboxylate.
 12. The process as recited in claim11 wherein said first catalyst is a potassium silanolate or a potassiumcarboxylate.
 13. The process as recited in claim 1, 2, 3, 4, 5, 6, 7, or8 in which said thermolysis catalyst is an alkali metal fluoride. 14.The process as recited in claim 13 wherein said thermolysis catalyst ispotassium fluoride.
 15. The process as recited in claim 1, 2, 3, 4, 5,6, 7, or 8 in which said heating is carried out in the gas phase and inwhich said temperature is 190° C. to 250° C.
 16. The process as recitedin claim 1, 2, 3, 4, 5, 6, 7, or 8 comprising the further step ofcontacting said fluorosilane with a metal hydroxide and water, at 0° C.to 100° C., to form a metal fluoride and a siloxane.
 17. The process asrecited in claim 16 wherein said metal hydroxide is sodium hydroxide orpotassium hydroxide.
 18. The process as recited in claim 17 wherein saidfluorosilane is trimethylfluorosilane or dimethylethylfluorosilane. 19.The process as recited in claim 1, 2, 3, 4, 5, 6, 7, or 8 whichcomprises the further step of free radically copolymerizing saidtrifluorovinyl ether.
 20. The process as recited in claim 1, 2, 3, 4, 5,6, 7, or 8 wherein (C₂ F₄) is --CF(CF₃)--.
 21. The process as recited inclaim 1, 2, 3, 4, 5, 6, 7, or 8 wherein said heating is done while inthe liquid phase and in the presence of a cocatalyst.
 22. The process asrecited in claim 21 wherein said cocatalyst is selected from the groupconsisting of crown ethers, linear polyethers, sulfones, and dialkylpyrimidones.